1. Field of the Invention
The present invention relates to a thermoelectric transducing material for forming a thermoelectric transducer adapted to perform thermoelectric cooling or thermoelectric power generation, and a method for producing the same.
2. Description of the Related Art
A thermoelectric transducer has a structure in which a certain number of pairs of junctions are formed by alternately joining a plurality of p-type thermoelectric transducing material and n-type thermoelectric transducing material, charge carriers of which are positive and negative, respectively, and one of each pair of junctions which forms, for example, pn junction along a current flowing direction and the other of each pair of junctions which forms, for example, np junction along the current flowing direction are spaced apart from each other. The thermoelectric transducer is used to cool by producing a temperature difference between junction regions according to electric current flowing therethrough or to generate electric power by generating electromotive force by providing a temperature difference between the junction regions. Heretofore, study has been made mainly of semiconductor materials such as Bi—Te, Pb—Te and Si—Ge as thermoelectric transducing materials, and some of them are being put to practical use in specific fields.
However, the performance of such a material is still insufficient to lead to full practical use in general consumer products and, hence, a thermoelectric transducing material exhibiting improved performance has been desired.
Recently, among oxide materials which have been considered unsuitable for thermoelectric materials, there have been found substances exhibiting high thermoelectric transducing performance characteristic such as layered cobaltite (of layered bronze structure) based NayCoO2 (y=0.2 to 1) (see Japanese Patent Laid-Open Publication No. HEI 9-321346). Though system of this type exhibit thermoelectric transducing performance close to that of Bi—Te, which is a semiconductor material of practical level, it is not yet clarified why such oxides exhibit high thermoelectric transducing performance characteristic. It is possible that the thermoelectric characteristic developing mechanism of such an oxide is different from that of a conventional thermoelectric semiconductor. If so, oxide materials of this type can be expected to exhibit higher thermoelectric transducing performance characteristic than conventional thermoelectric semiconductors.